1. Field of the Invention
The present invention is in the field of motorized wheel chairs, particularly, electric motor drivers attachable to standard wheel chairs to provide power to drive them.
2. Related Art
Substantial obstacles to mobility and everyday tasks of living continue for those who are disabled and bound to wheel chairs. There is a continuing need to make mobility for the wheel chair bound more reliable and convenient.
Motor drives for standard wheel chairs exist in the prior art. U.S. Pat. No. 5,494,126 to Meeker and U.S. Pat. No. 5,050,695 to Kleinwolterink Jr. describe motor drive units that may be attached to standard push wheel chairs.
U.S. Pat. No. 5,050,695 describes a geared brush type DC motor that is coupled to a very small drive wheel by a chain. It makes use of a fixed steering column. Only the height of the column can be adjusted to fit individual needs, by loosening a setscrew. The drive wheel is coupled to a frame though a bearing journal. The frame forms a well into which two large batteries are supported. Power is applied to the motor through a cable and is controlled with the control box at the top of the steering column. The speed and direction of the motor is controlled through wings attached to the control box. The wings are attached to simple switches inside the control box.
U.S. Pat. No. 5,494,126 describes an apparatus and method for attaching a motorized wheel to a wheel chair. This unit is attached to the front of the wheel chair through the use of two brackets bolted to the front tubes of the wheel chair. The steering column is telescopically connected to the drive wheel and held in place with a collar and a setscrew.
These devices are cumbersome in their operation, installation and transportation. The units are heavy and do not disassemble or collapse into a compact package. This creates difficulty in packing, as for example in the trunk of an automobile. Weight represents a substantial hardship, particularly for the elderly person, whose caregiver is commonly an elderly spouse. Prior art devices are also bulky and do not collapse into a small enough package for convenient transportation, again as in the trunk of a car.
The prior art units do not have batteries that are easily removable. Moreover, the batteries are not encased in a separate housing. Accordingly, separate packaging of the batteries is required to transport prior art batteries on public transportation such as commercial airlines. There is no provision for re-charging the batteries.
The prior art devices have in common a vertical shaft for holding a control module where the wheel chair occupant may reach it. This shaft is not movable, and accordingly obstructs ingress and egress from the wheel chair. The unadjustable vertical control shaft makes simple tasks difficult, such as pulling the chair up to the table, as for reading or a meal. These units are also difficult to install for a caregiver. They are prohibitively difficult for the disabled individual themselves to install.
The prior art devices have inefficient drive trains that use drive chains and further necessitate inefficient gearing and small drive wheels. Their systems are only 35% efficient. This inefficiency leads to a choice between either large, heavy batteries or smaller batteries that use an inordinate amount of power with an appreciably shorter charge life. Operational time between charges must be sacrificed. There is a need in the art for a more efficient drive motor and drive wheel operation.
In operation, the prior art units use small drive wheels that too readily transfer shock from minor impediments, such as a brick floor. Even slightly larger objects, such as a cobble stone street, become virtually impossible to traverse.
Further shortcomings of prior art devices include a lack of control precision when operating the wheel chair driver, particularly in tight spaces. Although it is known that wheel chairs are often used in enclosed or crowded spaces such as dining rooms, elevators, work places and the like, prior art drive units are only capable of travel at walking speed, without offering slower speeds for precise handling. The high torque and control sensitivity desirable for maneuvering in a crowded space at slow speeds is currently unavailable. There is a need in the art for a high torque, precise control system for operating wheel chairs at low speeds.
It is in view of the above referenced shortcomings that the present invention was developed.